<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var arr =  [1,2,3,4,5];
        //          0 1 2 3 4
        //将下标为2的元素修改成文渊
        var index = 2;
        arr[index] = "文渊"

        for(var i = 0 ; i < arr.length ; i++){
            console.log(arr[i]);
        }
    </script>
</body>
</html>